In many applications fluid flowing in a conduit may need to be treated by a treatment unit outside the conduit and then returned to the same. In such cases part or all the fluid is withdrawn from the conduit in correspondence of an upstream portion of the conduit, treated by the treatment unit and then returned to the conduit in a downstream portion of the same conduit. In certain cases it may be needed to withdraw the fluid from the downstream portion and return it to the upstream portion of the conduit. In these cases where the flow withdrawal and flow return areas may need to be switched, it can be convenient to adopt flow reversing systems which allow an easy commutation between the two configurations.
Referring by way of non limiting example to extracorporeal blood treatments, it is known removing blood from a patient by means of an arterial set, passing of the blood to a blood processing device such as a dialyzer, and returning of the blood to the patient again through a venous blood set. The venous and arterial lines create the communication of blood between a vascular access on the patient and the blood processing device. In order to monitor the patient access site it can be convenient to switch the arterial and venous lines between a first configuration, where blood is withdrawn from an upstream portion of the vascular access and returned to a downstream portion of the same, and a second configuration, where blood is withdrawn from a downstream portion of the vascular access and returned to an upstream portion of the same.
Also in this case it is useful adopting flow reversal devices which allow easy commutation between the two mentioned configurations without need of connecting and disconnecting the lines from the patient.
Devices capable of enabling flow inversion at the patient-side suction and delivery branches, while keeping the circulation flow within the filtering unit unchanged have been also developed.
A first known device is disclosed in the publication Kidney International Vol. 56, 1999, page 1564, FIG. 6 and in U.S. Pat. No. 6,189,388, again in FIG. 6, as well as in the French publication FR2889451 and consists in a set of four tube portions where 2 parallel tube portions are connected via two transversal tube portions. Clips are provided on each tube portion.
U.S. Pat. No. 6,695,807 and US2006161094 show flow reversal systems including arterial and venous lines+2 transverse tubes to form a square-shaped ring. A switching device can act on the square shaped ring to open and close selectively the four tube portions forming the ring.
U.S. Pat. No. 6,308,737 discloses an inverter device interposed between the vascular access to the patient and the blood pump, and the dialyser capable of enabling a flow inversion in the blood circuit portion directly in communication with the patient's vascular system while keeping the extracorporeal blood flow within the dialyser unchanged.
The inverter in particular comprises a deformable chamber provided with a plurality of ports. By deforming the chamber along a predetermined direction, a fluid communication between the pre-established ports is created while a fluid communication between other ports is prevented.
In particular, by suitably studying the connections of the extracorporeal blood circuit with the chamber doors and the deformations to be imposed to the chamber itself a flow inversion as above stated is obtained.
U.S. Pat. No. 5,894,011 discloses a device for flow inversion in haemodialysis apparatus. This device comprises two discs such interconnected that they can rotate relative to each other without separating. The two discs have appropriate fluid accesses, those of one disc being susceptible of connection with the blood lines directly associated with the patient and those of the other disc being susceptible of direct connection with the blood lines in fluid communication with the filtering unit. The two discs can take at least two relative angular positions; in a first position they enable passage of the blood flow in a first direction of direct circulation, in the other position (in which they are rotated relative to each other) they allow an inverted circulation flow in the circuit. In particular in the second inverted configuration the blood suction line from the patient in the first position becomes the delivery line of same and correspondingly, the delivery line of the first position becomes the suction line in the second position.
U.S. Pat. Nos. 6,177,049 and 6,319,465 disclose two further typologies of flow inverting valves both to be positioned between the vascular accesses to the patient and the blood pump and filtering unit. The first patent teaches use of a fixed external valve body to the inside of which an appropriate insert is connected which is capable of being moved between a first direct-circulation configuration and a second reverse circulation configuration. In particular, in the second reverse-circulation condition the suction line and delivery line at the vascular access to the patient are inverted with each other with respect to the first direct-flow condition. The second patent too shows a valve capable of exactly performing the same functions as the first patent, this valve being however made up of two halves coupled with each other so that they have a degree of freedom in rotation and, through mutual rotation of the two halves, a first direct-flow condition and a second reverse-flow condition are obtained at the vascular access to the patient.
US20060079827 shows a flow reversal valve having valve portions rotatably secured to one another, and detent features enabling audible or tactile feedback to a clinician or alignment features, such as visible indicators, on either side of the valve to confirm normal or reverse flow.
A further device for flow inversion in accordance with the U.S. Pat. No. 5,605,630 is also known. However this device is not used to invert the circulation flow at the vascular accesses to the patient, but to enable flow inversion within the filtering unit. In other words, the blood flow is inverted within the filtering unit intermittently and simultaneously the flow of the dialysis liquid is inverted within the same in such a manner that counter-current conditions are maintained therein. The above is carried out for quite different purposes from those of the present invention, i.e. to avoid blood clotting within the filter for dialysis.